The present invention relates generally to pressure activated switch devices and touch panel devices, and to materials useful for closing and opening electrical connections in such devices due to the application or cessation of pressure.
Touch screens and membrane switches provide convenient user interface devices that can be activated by a touch such as from a finger, stylus, or other appropriate object. In many applications, these devices function by detecting a signal when otherwise separated conductive films, electrodes, or circuits are brought together under the application of pressure by the user.
The present invention provides a switchable pressure activated electronic device that includes a first conductor that is movable toward a second conductor and a composite material disposed between the first and second conductors for electrically connecting the first and second conductors under application of sufficient pressure therebetween and for electrically isolating the first and second conductors in the absence of such sufficient pressure. The composite material includes a plurality of conductive particles at least partially embedded in an electrically insulating layer. The plurality of conductive particles have no intended relative orientation and are disposed so that substantially all electrical connections made between the first and second conductors are through single particles.
The present invention further provides a switchable pressure activated electronic device that includes a composite layer that includes a plurality of substantially spherical conductive particles disposed so that substantially none of the conductive particles are in physical contact, where the composite layer is disposed between two conductors and has a thickness that reversibly decreases upon application and cessation of sufficient force applied between the conductors to allow electrical connection of the conductors through one or more of the conductive particles during application of sufficient force and to allow electrical isolation of the conductors during cessation of sufficient force.
The present invention also provides a switchable pressure activated electronic device that includes a first conductor, a second conductor, means for electrically connecting the first conductor to the second conductor upon application of sufficient pressure, and means for electrically isolating the first conductor from the second conductor upon cessation of sufficient pressure.
The present invention still further provides a method of making a switchable pressure activated electronic device that includes dispersing a plurality of conductive particles, at least partially embedding the conductive particles in a layer of insulating material, and disposing the layer of insulating material and conductive particles between a first conductor and a second conductor so that the first and second conductors are electrically connected through one or more single particle contacts upon application of sufficient pressure, and the first and second conductors are electrically isolated upon cessation of sufficient pressure.
The present invention further provides a film for use in an electronic switch that has a thickness that reversibly decreases with pressure, and that includes a plurality of randomly positioned conductive particles at least partially embedded in the layer. The particles are distributed so that, for substantially all positions across the layer, there is at most a single particle through the thickness of the layer.
The present invention yet further provides an electronic switch that includes a first conductor that is movable toward a second conductor, and a plurality of substantially randomly positioned conductive particles disposed between the first and second conductors, where the first conductor is electrically isolated from the second conductor in the absence of sufficient pressure therebetween and the first conductor in electrical contact with the second conductor through one or more single particle connections when sufficient pressure is applied therebetween.
Also provided is a display system that includes a display viewable through an electronic switch of the present invention.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.